Existing resolution enhancement schemes improve text quality by using algorithms or look-up tables which determine whether an initial text pattern stored in a memory should be modified to correct for quantization limits. This determination of whether an initial text pattern should be modified requires a prior knowledge of acceptable text patterns usually found in alphanumeric text. The correction scheme then modifies the initial text pattern according to a set of rules. The corrected and now more pleasing text pattern is then printed or otherwise displayed at a higher resolution than the initial text pattern stored in the memory. Such resolution enhancement techniques may be performed by circuitry residing in a high resolution printer.
The above enhancement scheme, which provides smoother edges by reducing quantization errors, is not as effective on graphics, since the quality of many graphics patterns is dependent on the quality of the halftone patterns making up the graphics pattern rather than on any edges in the graphics pattern. Thus, these graphics patterns are usually not changed from their initial form.
It is understood that a low resolution halftone graphics pattern presents a coarser and less pleasing halftone pattern than a high resolution graphics pattern. However, a high resolution pattern created by simply printing each dot of a low resolution graphics pattern as a fixed number of smaller, high resolution dots (i.e., a cluster of dots) would still contain equivalent quantization errors and present a coarse halftone pattern.
What is needed is a graphics enhancement scheme to improve the quality of a low resolution graphics pattern when printed by a higher resolution printer.